Facile and Efficient Synthesis of Dendrimers and One-Pot Preparation of Dendritic–Linear Polymer Conjugates via a Single Chemistry: Utilization of Kinetically Selective Thiol–Michael Addition Reactions

Abstract

A kinetically selective thiol–Michael addition “click” reaction was employed for facile and efficient synthesis of dendrimers as a first example of using solely a single chemistry without protection/deprotection reactions in dendrimer synthesis. First, a wide range of thiols and vinyls were assessed for their reaction selectivity, and several combinations demonstrated superior selectivity. This result led to a design of new monomers A*A2 (vinyl) and B*B2 (thiol) that both have three functional groups with one much more reactive and two much less reactive moieties. Starting from a multifunctional core thiol, a fifth-generation dendrimer with 96 peripheral functional groups was synthesized in less than a half day by sequentially reacting A*A2 and B*B2 monomers all under thiol–Michael addition reaction conditions. Furthermore, a one-pot dendritic–linear polymer conjugation was demonstrated by a convergent synthesis approach starting from an alkyne-terminated dendron synthesis that was subsequently coupled with azide-terminated poly(ethylene glycol), all in one pot with just a single, final purification step needed for the entire procedure. The results herein will provide a new, robust, and efficient methodology for synthesis of dendrimers as well as other complex polymer architectures such as dendritic–linear polymer conjugates, heterofunctional dendrimers, and dendronized surfaces.